Extruders are often used in the preparation of various food products and especially in the preparation of ready-to-eat ("RTE") cereals such as puffed. Extruders, especially cooker extruders, are desirable because a single machine can produce large quantities of a cooked cereal dough in a short period of time. Such cooker extruders can be used to prepare cooked dough extrudates which can thereafter be formed into individual cereal or snack pieces, with the formation of such pieces possibly involving puffing the pieces to form finished puffed RTE cereals. In another variation that is increasingly popular, the conditions of the extruder and the cooked cereal dough are such that the dough puffs immediately upon being extruded and is cut into individual puffed pieces at the die head. Such a process is referred to generally as "direct expansion."
While the preparation of a puffed or "direct expanded" extrudate is desirable, it may be desirable to produce a variety of products having different colors, flavors, or similar additives. For example, RTE cereal blends that comprise a mixture of differently shaped pieces are desirable, with each shape having a distinctive color and/or flavor.
In current practice, in order to produce an RTE cereal blend of distinctive colors, shapes or flavors, a sequence of individual color/flavor runs are made. The product from each run is collected and subsequently admixed to form the blend. For instance for a direct expanded product, a first colored cooked cereal dough is prepared by adding color to the starting material or by injecting a color into the dough upstream of the dieface. The colored dough is directly expanded through a shaped dieface and face cut as it expands to form individual pieces. To prepare, for instance, a second color and shape, the first color injection is discontinued and a second different color material is injected into the cooked cereal dough. To prepare a second shape, the first die head is removed and substituted with a die head having the desired second shape.
While effective, one problem with this conventional practice resides in the generation of unusable scrap material during the color addition transition as the new color is admixed with the residual amounts of the prior color. Still more scrap is generated as the extruder comes up to steady state conditions after the second color run is started. A second problem is that the various colored pieces must be collected in large batches to be admixed at a later time to form the blended RTE cereal. The properties (e.g., plasticity, temperature, moisture content, starch conditions, frangibility, etc.) of the finished pieces may deteriorate over the storage period. A third problem relates to the broken pieces, dust and/or cereal fines created by the admixing step.
It would thus be desirable to be able to provide at least two and preferably a multiplicity of streams of cooked cereal dough from a single extruder, with each of the streams having a distinct color, flavor and/or similar additive.
In even a more preferred form to increase novelty and market appeal, the finished pieces would have at least one zone having a color, flavor, and/or similar additive distinct from the remaining zones of the finished piece.
Accordingly, it is an object of the present invention to provide apparatus and methods for providing a plurality or multiplicity of dough streams from a single extruder wherein each of the streams has a distinct color and/or flavor.
It is further an object of the present invention to provide apparatus and methods for providing a plurality of dough streams having a distinct color and/or flavor where a portion of one of the streams is bled off and introduced into at least another stream to form a finished piece of distinct zones.
While color injection into a cooked cereal dough is well known, another problem resides in the complete blending of the color into the dough without changing the properties of the dough by imparting significantly more shear into the dough.